1. Field of the Invention
The present invention relates to a valve apparatus capable of regulating opening of a valve for opening and closing a passage.
2. Description of Related Art
Conventionally, a diaphragm type fuel pump, in which an intake/discharge pumping action is performed by activating a diaphragm using pulsation pressure of an engine, is used as a fuel supply apparatus for supplying fuel from a fuel tank to a fuel injection apparatus or the like. Japanese Unexamined Patent Application 2002-202026 is known as an example of a conventional diaphragm type fuel pump, structure of which is shown in FIGS. 3 and 4. A fuel pump 10 is constituted by a pump body 16 formed with an intake port 12 and a discharge port 14, shown in FIG. 3, a bottom body 18 disposed on one of side faces of the pump body 16, a cover 20 disposed on another side face of the pump body 16, a diaphragm 22 sandwiched between the pump body 16 and bottom body 18, and a membrane 24 sandwiched between the pump body 16 and cover 20. The pump body 16, bottom body 18, and cover 20 are formed using a synthetic resin material which is capable of plastic deformation under application of heat, but may be formed from metal.
A pump chamber 26 is formed between the diaphragm 22 and pump body 16, and a pulse chamber 28 is formed between the diaphragm 22 and bottom body 18. A pulse introduction passage 30 for introducing a pulse pressure generated by an engine, not shown in the drawings, into the pulse chamber 28 is formed in the bottom body 18, and the pulse pressure is introduced into the pulse chamber 28 through the pulse introduction passage 30.
A fuel intake chamber 32 and a fuel discharge chamber 34 are formed between the membrane 24 and pump body 16. A damper chamber 36 which opposes the fuel intake chamber 32 via the membrane 24, and a damper chamber 38 which opposes the fuel discharge chamber 34 via the membrane 24, are formed between the membrane 24 and cover 20. The fuel intake chamber 32 communicates with the intake port 12 shown in FIG. 3, and the fuel discharge chamber 34 communicates with the discharge port 14 shown in FIG. 3.
An intake communication passage 40 connecting the fuel intake chamber 32 and pump chamber 26, and a discharge communication passage 42 connecting the pump chamber 26 and fuel discharge chamber 34, are formed in the pump body 16. A check valve 44 formed from a flexible material for opening and closing the intake communication passage 40 is attached to the pump body 16. The check valve 44 serves to move fuel only from the fuel intake chamber 32 into the pump chamber 26. A check valve 46 formed from a flexible material for opening and closing the discharge communication passage 42 is also attached to the pump body 16. This check valve 46 serves to move fuel only from the pump chamber 26 into the fuel discharge chamber 34. The check valves 44, 46 are fixed to the pump body 16 by rubber grommets 48.
As shown in FIG. 5(a), a hole 50 for inserting a part of the grommet 48 is formed in the pump body 16 in the vicinity of the intake communication passage 40 and the discharge communication passage 42. The grommet 48 is formed by integrating a head portion 52 on one end side, a stopper portion 54 on another end side, and a neck portion 56 joining the head portion 52 and stopper portion 54. An outer diameter of the head portion 52 of the grommet 48 is set to a larger dimension than an inner diameter of the hole 50 in the pump body 16, but such that the head portion 52 of the rubber grommet 48 can pass through the hole 50 in the pump body 16 when pushed into the hole 50 forcibly. An outer diameter of the stopper portion 54 of the grommet 48 is set with a larger diameter than the head portion, and has a shape and dimensions which prevent it from passing through the hole 50 in the pump body 16 even when pushed into the hole 50 forcibly. The check valve 44 formed from a flexible material takes a disk form having a central hole 58. An inner diameter of the hole 58 in the check valve 44, 46 is set to a smaller dimension than the outer diameter of the head portion 52 of the grommet 48.
A procedure for attaching the check valve 44, 46 to the pump body 16 is shown in FIGS. 5(a) and 5(b). First, the head portion 52 of the grommet 48 is inserted into the hole 58 in the check valve 44, 46, thereby attaching the check valve 44, 46 to the grommet 48. Then, the head portion 52 of the grommet 48 is inserted into the hole 50 in the pump body 16. Thus, the pump body 16 and check valve 44, 46 are sandwiched between the head portion 52 and stopper portion 54 of the grommet 48. As a result, the check valve 44, 46 is attached to the pump body 16. When the check valve 44, 46 is attached to the pump body 16, the intake communication passage 40 or discharge communication passage 42 is closed by the check valve 44, 46.
In the diaphragm type fuel pump shown in FIG. 4, by introducing a pulse pressure generated in a crank chamber (not shown) of an engine into the pulse chamber 28, the diaphragm 22 performs an alternating stroke movement between pump chamber 26 side and pulse chamber 28 side. By virtue of this stroke action of the diaphragm 22, fuel that is introduced into the fuel intake chamber 32 from a fuel tank, not shown in the drawings, enters the pump chamber 26, passes from the pump chamber 26 into the fuel discharge chamber 34, and is discharged to a fuel injection apparatus or the like.
A diaphragm type fuel pump comprising a check valve attached using a conventional attachment structure has the following problems.
(1) Operations are required to insert the head portion 52 of the grommet 48 into the hole 58 in the check valve 44, 46, and to insert the head portion 52 of the grommet 48 into the hole 50 in the pump body 16, and therefore a large number of steps is involved in an operation for attaching the check valve 44, 46 to the pump body 16.(2) The grommet 48 is made of rubber, and therefore deteriorates when it comes into contact with fuel.(3) To fix a central position of disk-form check valve 44, 46 to the pump body 16 using the rubber grommet 48, an inner diameter of neck portion 56 of the grommet 48 must be increased to a certain extent. Accordingly, an outer diameter of the disk-form check valve 44, 46 must be increased, and as a result, a size of the pump itself increases.(4) A fuel intake amount and fuel discharge amount passing through the intake communication passage 40 and discharge communication passage 42 are determined by a passage diameter of the intake communication passage 40 and discharge communication passage 42, and pulse pressure that is generated by the engine and introduced into the pulse chamber 28. However, with a constitution in which the check valve 44, 46 is fixed to the pump body 16 by the grommet 48, the check valve 44, 46 curls up greatly from the intake communication passage 40 or discharge communication passage 42 when the pulse pressure is great (see dot-dash line in FIG. 5), with a result that a valve lift amount of the check valve 44, 46 cannot be restricted.
Due to these problems (1) through (4), it is difficult in the conventional diaphragm type pump shown in FIG. 4 to reduce a size of the pump itself, and desired performance cannot be obtained.